Answer: 2 n² − n.
- A 2<sup>n</sup>
- B n²
- C 2<sup>n² − n</sup>
- D 2<sup>n²</sup>
Correct answer: C. 2<sup>n² − n</sup>
Explanation: The n diagonal pairs are forced to be present; the remaining n² − n off-diagonal pairs are free, giving 2<sup>n² − n</sup>.
Concept context
Types of relations, equivalence classes, one-one and onto functions, composition, and invertible functions